When using plain CSS, css variables have been made available in colors.css, you can use these by simply importing the file and using the variables like so
.mydiv {
background-color: var(--ens-grey1);
color: var(--ens-blue);
}
For styled-components it is recommended to use the [ensdomains/thorin] global-styles. You can import these like so
import { ThorinGlobalStyles } from '@ensdomains/thorin';
import { baseTheme, lightTheme, darkTheme } from '@ensdomains/thorin';
For tailwindcss it is recommended to use the provided tailwind.config.js file. Simply drop it in your project and you should be good to go!
.bg-ens-blue
.bg-ens-gradient-blue